This is probably my favourite animal name since the ultimate shrew.

No it’s not a translation error, and I can hear several birdwatchers tutting that “rail” is in fact a common sort of bird, including some members of the coot family. Fair enough.

But the world’s smallest flightless bird is indeed Inaccessible with a capital “I”.

To find it, you first need to travel by boat over the Atlantic Ocean, pretty much until you reach the mid-point between Africa and South America.

Imagery © 2020 NASA, TerraMetrics, Map data © 2020

Here sits the island chain of Tristan da Cunha – Saint Helena to the British – and within it, an extinct volcano with sheer cliffs known as, wait for it, Inaccessible Island.

Once you make landfall, you’ll probably see the one solitary human hut from an expedition in the 1980s, as well as the odd apple tree from colonisation attempts in the 1930s.

If you’re lucky, you’ll also spot the dark, shifting forms of the Inaccessible or Inaccessible Island rail, dabbing at foliage for earthworms and bugs and scuttling away under it. It’s found nowhere else in the world, and if Fraser et al.‘s 1992 study is anything to go by, you’ll probably hear it first.

It’s a bird between two worlds, literally.

As well as the Africa-South America straddling, it’s found a rather strange niche for itself on the island. Its small, dark and rounded wings are useless for flying, but it can walk within two hours of hatching and leave its nest within a day.

Photo by Brian Gratwicke.

It’s a fairly agile climber thanks to its large thumb claw, and its speed and foraging habits mimic a mouse rather than a bird. At the same time, it’s exponentially louder.

Living in small family groups of 5 where Mum and Dad share the feeding and incubation, it keeps in constant vocal contact with its relatives, and gives the odd alarm call if a subantarctic skua or Tristan thrush happens to fly overhead.

Other than these two rascals it has no other predators on the island – hence shrugging off the bane of flight – and when faced with an egg-counting human researcher, rather than beating a retreat, it just becomes increasingly difficult to lift off its nest. So you can imagine the havoc a rat, or god forbid a cat, could wreak should one ever escape on to the island.

It looks like it’s already suffered enough.

Fortunately, Inaccessible Island was made a nature reserve in 1994, and is a UNESCO World Heritage Site together with Gough Island. Tristan islanders are allowed to visit and gather fruit and guano, but they have to be careful of any other mammalian stowaways for that reason.

But now to your burning question: how on earth did a small, flightless bird find its way on to an inaccessible island in the first place?

This was a bit of a head-scratcher until a couple of years ago. Initially, its discoverer Percy Lowe, head of ornithological collections at the British Museum, thought it had wandered across a sunken land bridge in the Atlantic, but then plate tectonics pulled that theory to pieces.

After a bit of DNA pokery, we discovered it was descended from a group of South American dot-winged crakes (Porzana spiloptera) who colonised Inaccessible Island in one fell swoop about 1.5 million years ago. Fortunately, that was 4.5 million years after the island stopped chucking lava about.

They either flew, or arrived via floating debris, possibly during stormy weather, and since there were no nasties on the island, later shrugged off their ability to fly.

Now we know its origin, we might need to change its name. But not the one that hurtfully points out a man-made and unreachable perch.

The first half of its Latin name, Atlantisia, is after Atlantis, due to the old land bridge theory. But its genetic results should probably plop it in another pre-existing rail genus, the less pretty and more geometric-sounding Laterallus lot from South America.

Well, given it lives on an epic island with plenty of food, few predators, and just the occasional annoyance of being lifted off its nest, it needs something to complain about.

TLDR

Latin: Atlantisia rogersi

What? The world’s smallest flightless bird.

Where? The island Inaccessible, Tristan da Cunha/Saint Helena, in the south Atlantic between Africa and South America.

How big? About 13-15.5 cm / 5-6 inches long.

Endangered? Considered Vulnerable as it’s only found on this one island, and can’t exactly fly away from danger.

Probable motto: I live on a kickass volcano with no predators. Why would I want to fly anywhere?

Aww they look cute. Do they need my help at all?

Being isolated is always a risk, but their island is already a nature reserve with no humans, so given the circumstances it’s fairly safe.

Just to prove I’m not fibbing:

BirdLife International. 2016. “Atlantisia rogersi The IUCN Red List of Threatened Species” 2016: e.T22692556A93358821.

Editors of Encyclopaedia Britannica. No date. “Saint Helena“. Britannica.com.

Fraser, M.W. et al. 1992. “Observations on the Inaccessible Island Rail: Atlantisia rogersi: the world’s smallest flightless bird“. Bulletin of the British Ornithologists’ Club 112(1):12-22.

Kliman, Richard. 2016. “Encyclopedia of Evolutionary Biology“. Volume 1. Academic Press/Elsevier.

Lindblad Expeditions-National Geographic. 2012. “Seldom-visited Nightingale and Inaccessible islands“. YouTube.

Montgomery, Sy. No date. “Rail“. Britannica.com.

News Staff. 2018. “Scientists Crack Mystery of World’s Smallest Flightless Bird: Inaccessible Island Rail“. SciNews.

Oskin, Becky. 2017. “What is plate tectonics?” LiveScience.

Stervander, Martin et al. 2019. “The origin of the world’s smallest flightless bird, the Inaccessible Island Rail Atlantisia rogersi (Aves: Rallidae)“, Molecular Phylogenetics and Evolution 130:92-98.

Taylor, Barry. 1998. “Rails: a guide to rails, crakes, gallinules and coots of the world“. Pica Press Sussex.

Taylor, B. & Sharpe, C.J. 2020. “Inaccessible Rail (Atlantisia rogersi)“. In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona.

Tristan da Cunha Government & Tristan da Cunha Association. No date. “Inaccessible Island“. Tristan da Cunha Website.

Trowbridge, Leann. No date. “South Atlantic Ocean, about half way between southern Africa and South America“. WWF.

Featured image credit: “Inaccessible island rail”, by Brian Gratwicke.